The perils of joint tenancy
by BlackEyedGirl
Summary: “Wow. So this is what an out of body experience feels like.” Mostly preslash, shameless exploitation of scifi cliche.


**Title:** The perils of joint tenancy  
**Fandom:** Eureka  
**Pairing:** Jack/Nathan  
**Rating:** PG-13 (maybe mild R for one explict reference)  
**Genre:** Drama  
**Length:** 4,600 words  
**Disclaimer:** All belongs to the Sci-Fi channel and people not me.  
**Warnings/Spoilers:** Through the end of S1, but none from S2, which hasn't aired where I am yet.  
**Summary:** "Wow. So _this_ is what an out-of-body experience feels like." Mostly pre-slash, shameless exploitation of sci-fi cliche.

* * *

"Wow. So _this_ is what an out-of-body experience feels like." 

"This isn't an out of body experience."

"Why the hell not? I'm out of my body."

"Because you're in _mine_!"

Jo looked at them, and tapped her foot. After moment she conceded, reluctantly, "Okay, that's weird."

Jack's body lay, looking asleep, on the bed to the left. On the right, Nathan Stark was busily having an argument with himself. Or, to those members of the population who were inclined to believe Fargo, Stark and Carter were arguing with each other. Through the same mouth.

"How did this _happen_?" Alison demanded.

"Ask him," one of them said. The flip tone suggested Nathan, but the wide-eyed disbelief seemed more like Jack.

Fargo came to her rescue. "We had… a slight… malfunction with the bioelectronic storage prototype."

"The brain drain?" Nathan_Jack _asked.

"How do you even know what…" Jack_Nathan _said.

The brain dr… bioelectronic storage device was intended, eventually, as an answer to some forms of degenerative diseases. Eventually. When they had figured out how to cram the room-sized prototype into someone's head, or found someone who didn't mind that the cure for their MS was to store them in a metal cube. Also, the device had fried a few of the monkeys.

What it was not intended to do, however, was transplant one personality into the body of someone else. And it _really_ wasn't meant to force their sheriff into the same body as the head of Global Dynamics. That was just the icing on the cake.

"Fargo?" Alison said.

"They touched it!"

"Fargo…"

"At once! I really can't be expected to anticipate-"

"Fargo!"

"We're working on it."

"You've called-?"

"Henry? Absolutely. No problems at all, we'll have everyone back where they should be before you can-"

"Fargo."

"Shutting up now."

Henry's arrival didn't help them get anyone back where they should be, but Fargo started breathing normally again, and Alison felt able to resist the urge to throttle someone. Somewhere between Nathan impugning Jack's intelligence and Jack making not-so-cryptic remarks about doctorates as a substitute for other attributes, the expression "killing two birds with one stone" had seemed horribly apt.

Henry had stared for a minute, laughed for three more, and then started poring over the readouts from the machine. Five hours later, however, they didn't appear to be any closer to a solution.

"Is there anything more we can do tonight?" Jack asked.

"Well obviously I'd like to-"

"We should really-"

"Anything that will help us in any way that can't be better achieved tomorrow after a full night's sleep on my contour mattress?" he said.

Fargo and Henry shook their heads, but Nathan turned slowly (looking at what, Alison wondered - the voice had come from his mouth) and quirked an eyebrow. "And what makes you think we're going to your bunker? I have a perfectly serviceable bed with a more than serviceable mattress in my own house."

Nathan's smooth expression pulled out into Jack's anger and Jack's arms held up in disgust. "Because I have a fifteen year old daughter who doesn't know why her father hasn't come home yet."

Nodding without speaking, Nathan accepted defeat. He stumbled on the way out of the door and it was Jack that snapped, "Just let me drive, Stark."

- - - - -

By the time they made it to the house, Stark had recovered his equilibrium enough to be making Jack miserable. He was letting Jack do the walking – it was his house and his daughter – but every so often he'd twitch one finger, or one toe. Just enough to be annoying, and distracting enough that Jack nearly tripped on the way down the steps. It was some freakish Stark-ish proof of dominance and Jack really wasn't having a good enough day to play along with that.

"Do that again," he said, facing upwards into SARAH's camera, "and I'll ram your head into the door."

"You realise," Stark drawled, "that doing that would hurt you as much as it would hurt me?"

"Yeah, but tomorrow Henry'll get me back in the right body and your nose will still be broken."

"A little on edge, Sheriff?"

"Yeah, cause this is all in a days work for you."

"Honestly?"

They were interrupted by the door swinging open with its usual burst of air.

Zoe stood up hurriedly from the couch. "Dr Stark?"

Jack took a deep breath, and tried his best. "Zo, this is going to require a leap of faith on your part but-"

Her eyes widened. "Dad?"

"Or maybe it won't."

"Oh please, like bodyswap _wasn't_ on the list? We should have codewords, you know that, right?"

"Zoe."

"Clones, robot doubles, possession, hypnosis, _alien possession…_"

Zoe's list of potential calamities had actually turned into something of a bingo card lately – it seemed they crossed off a disaster pretty much every week. Out of body experience would have gotten him a line, but Stark had squashed that plan. And she was right about the codewords.

"You were thirteen," he said, wickedly. "Your mom was of town and it was just you and me. You had to come and tell me that you were out of-"

"Dad!" Her furious blush spread from her cheeks outwards.

"Now you know it's me."

"I knew it was you because you were _talking to yourself_ outside our front door. Stark would just have burst straight in."

"Zoe."

"What's up with that anyway? I mean, you…"

"Zoe! Body_swap _may have been overstating it slightly. It's more of a joint tenancy."

"So he's…"

Stark chose that moment to wrest control back. "Indeed. Now, fascinating as this all is, I'd like to get some sleep so we can undo it as quickly as possible. I can feel my IQ dropping as we speak."

Jack had a strong suspicion that from the outside it looked pretty ridiculous – Nathan walking away with his body while Jack tried to stop him. Something like invisible hands pulling him in two directions. Zoe's eyebrows raised in comical amusement.

They were halfway to the bedroom before Jack regained enough control to say, "A) Don't talk to my daughter like that. B) Do I want to know how you know where my bedroom is?"

Either their brains were doing some kind of melding, or Carter was getting better at translating Stark's dismissive noise into the swearing he rarely resorted to.

"Yeah," Jack muttered, "this is going to be fun."

- - - - -

Between Carter and Nathan, they had quite a caffeine dependency, and even SARAH struggled to keep up. It wasn't helping that with his own dreams of world domination and Carter's nightmares of apocalypse, they hadn't got much sleep.

Also, it turned out that their perennial 'my job beats your job' argument became more complicated when, really, only one of them could win.

"I save _lives."_

"You save cats from trees."

"It wasn't a cat. It was, by that point, the size of a small lion. And I was saving the Baker twins from being mauled by it. What did you do yesterday?"

Nathan thought for a second. "Well, I _was _working on a project that could improve the lives of billions of people suffering from degenerative diseases. Then you came to visit me and then… well I don't quite remember what happened after that."

"You're saying you have work to do."

"Yes."

"More important than mine."

Nathan tried to convey with a raised eyebrow that the previous assertion had been implied. It was a move only slightly hindered by the fact that they were currently sharing a face. "My body, my rules."

The argument continued up until the point that Zoe coughed.

Raising her (pilfered) coffee mug, she screwed up her nose. "When are you guys going to get this fixed? Because I'm starting to lose track of which one of you is speaking."

If that wasn't enough to get them moving towards the labs, nothing would be.

- - - - -

Zoe's fairly terrifying pronouncement followed them all the way to Global Dynamics, where Henry, Fargo and Alison were waiting.

Nathan didn't bother with pleasantries, and in fact did his best to stop Jack even nodding hello. He looked over the readouts from the day before, and then started writing.

"Ow."

Alison looked at Jack in concern. "What's wrong."

"Much as I hate to say this – Stark thinking that quickly is actually making my head hurt."

She smothered her laughter under a cough. "Really."

Henry's grin was wide and teasing. Jack could already predict the mileage that they were going to get from this one.

Stark, though, just continued to write busily on the board, not even breaking concentration long enough to mock. Jack had got the hang of tuning him out now – which just went to prove that a person really could get used to anything. Even a multiple-doctorate-having genius doing algebra in one half of a brain while you used the other to make jokes. Jack couldn't tell if Stark was even listening.

"It's a little difficult not to," Nathan muttered, wiping out a swathe of equations in a stroke.

Jack froze suddenly enough that Stark's next pen movement screeched to a halt.

"What?" Nathan asked.

"You're reading my mind now?"

"Excuse me?"

"You replied to something I didn't say out loud."

"No I didn't."

"Yeah, you did."

"I think I would know if I…"

Alison coughed, and tapped her foot. "Guys, is there a reason we've stopped working?"

Jack didn't know which one of them decided to spin around, but it was him who said, "Are you even hearing this?"

Henry stepped closer to them, frowning now. "Neither of you were saying anything."

- - - - -

They had been in Global Dynamics until the early hours, and were still no closer to working out how to undo it, or what was making it get worse. Accidental telepathy might sound fun, but if there was anyone Jack didn't want a mental bond with, it was Nathan Stark.

The house was dark and still by the time they got in, and SARAH's "Good night Sheriff Carter, Doctor Stark," was barely more than a whisper.

Jack averted his eyes as far as was possible while Stark got undressed and laid down on the bed. He sighed deeply, and prepared to try and get to sleep. This was, naturally, when Stark decided to slide his hand down and under his boxers.

"Nathan!" Jack hissed.

"Yeah?" Stark said calmly.

"Nah uh. No way are you doing what I think you're doing."

"It's been a long day, Sheriff."

"I know. I was there!"

"So you understand. Good."

"You do realise this is assault?"

"My hand, my dick."

"My brain! Permanent scarring mental images!"

"Close your eyes."

"Close my… do you hear yourself when you speak?"

"Apparently neither of us need to speak right now."

Jack wrested the hand above the covers. For reasons he had yet to speculate about, he had more control over Stark's body than Stark did. Which might have been why the other man was so pissy. If it was anyone else, at any other time, he might sympathise. Instead, he tried his best to send a bombardment of the least erotic things he could think of to Stark's side of the brain. Unfortunately, to balance things up, Stark was finding it much easier to tune Jack out.

Still, Nathan stopped trying to move after a second or two. "Relax, Carter. If you feel that strongly about it…" He trailed off, and drifted into something like sleep.

How was it that even when Jack knew he had won, it still felt like a loss?

- - - - -

But it would always be Carter who came out of the explosion with the scientist over his shoulder, glaring at Nathan as if it was all his fault.

"It generally is your fault," Carter said, evidently having caught the end of that thought.

"Will you stop that?"

"Stop what?"

"Stop prying."

"Oh, now I'm the one being inappropriate? After last night? And you're the one going wandering round my thoughts for fun."

"I am not…"

"How would you like it if I did that?"

"You just…"

"I mean, I could be just as annoying. I could take advantage. I could walk out this door right now."

Nathan sighed, and threw his hands up in frustration. "And go where, Sheriff?"

"Oh, I don't know, Section 5, maybe? Who's gonna stop Nathan Stark walking in to have a look at his precious artefact? Precious enough to risk lives for anyway, and that one was nothing to do with-"

Their voices got louder and louder. Nathan could hear Alison in the background trying to talk them down. He didn't listen. "Yes, Carter, some of us have secrets a little more interesting than worries over whether we're a good father or a bad husband, or not _smart enough_ to be in Eureka. Some of us…"

"Get the fuck out of my head."

"It's my head." And he reached in. Not just skimming the surface, but digging, dragging up memories haphazardly. The ones he had caught before, because Jack was so open and so light and the worst things he thought of were all of himself, and untrue. That he was a bad father to Zoe, that his marriage breakdown was all his fault, that he was going to get someone killed in Eureka because he wasn't a genius. Nathan could so easily resent those small concerns, drawn into something monstrous in Carter's mind.

Then he caught one of the others. _Alison, pregnant, her hand resting on her stomach. _"Carter?" _The valedictorian of the class of 2010, Zoe Carter. A tornado out of time. _"Carter?" _'Someone?' 'Okay, me.' Four years gone and an empty bed. 'If you do this, the world will unravel.' _"Jack?"

But Carter had gone silent in his head. "Jack, what the hell happened? What did you do?"

Alison and Fargo were staring but Henry was braced against the wall – he had known what might happen. Nathan took a step towards Henry but he bolted for the door and Jack stopped Nathan from following. He still wouldn't speak.

- - - - -

For the rest of the day, Nathan spoke, and Jack walked them from place to place, and wouldn't talk back. Henry hadn't returned, and Fargo was getting nowhere on his own.

So they were back at the smart-house in time for dinner, where Zoe's chatter made up for the lack of noise elsewhere.

She was complaining about her homework. "Like it's not enough that I have to learn advanced physics that I'm never going to need, I need to learn about all the dead physicists too? Who in their right mind made History of Science a compulsory class?"

"That would be me," Nathan answered, barely aware of doing so.

Zoe was quiet for a second, obviously debating how far she should push him. Then: "Um, _why_?"

"Because it's important. Most of the children in that school are going to go on to work in places like Global Dynamics."

"And?"

"And I would like to be sure that they know who they're following after when they decide to destroy the universe. They'll have the world at their fingertips and they should understand what people sacrificed to get them there. What they suffered, so we can work here in peace. It's…"

"Important," she completed quietly.

"Yes."

She leant her elbows on the table, and looked at him seriously. "So tell me about it."

So he did. About Galileo, who had known he was right but recanted in the end. Oppenheimer who would be remembered for one piece of a body of brilliant work – one thing he would later argue against, and be called a traitor for doing so. Turing, who had helped his country win a war and was forced to suicide because they didn't like what he did in the peace. Archimedes, who had given the town its name, who had been killed because he had refused to surrender until he had solved his problem. Newton who had known, as they all should, that they were standing on the shoulders of giants.

She smiled at him when he stopped, and put her hand casually on his shoulder. "Thanks, Nathan." She was gone with a flash of blonde hair.

Jack cleared his throat. "Let's go to bed."

Lying in bed, too many thoughts vied for his attention. That Jack thought Kim's death was his fault, and that Henry had been stupid enough to try and undo it, knowing what might happen. That their perfect world didn't have him in it. He had thought he was doing good.

"You're just really bad at this, aren't you?" Jack asked.

"I'm sorry?"

"Switching off."

"It's been an exceptionally long day."

Jack laughed, and Nathan didn't try and find out why. Jack said, "Close your eyes, Nathan," and reached down.

"Jack…"

"Yeah, I changed my mind. If anyone asks, I really needed to get to sleep."

"That wasn't…"

"You're right-handed, yeah?" Jack switched to his left.

Nathan closed his eyes. Jack's hand was a little awkward – he was right-handed too – but it felt like _Jack's hand_, and that was what mattered. It wasn't him, trying to piss Jack off, or trying to calm himself down. It was Jack, slowly running a hand up and down his dick until he chased away all other thought.

Afterwards, both of them slept, and neither remembered the dreams.

- - - - -

"Huh?"

"I'm not saying I'm going in for the brown and tan thing, but I'm pretty sure even you have to turn up to work one day in three."

Jack shrugged, and nodded, and walked them to his office without further comment.

There was a pile of reports sitting on the desk. Jack groaned. "Maybe we should have picked up some coffee first."

The file on top was the standard form for a lab accident causing non-permanent serious physical alteration to a member of the facility. Below it, ominously, were the forms for permanent alteration, and fatal alteration. For a change of pace, Jo had also thrown in the one for drug induced shared psychosis.

"Does this actually count as physical alteration?" Jack asked. "I would have thought it was mental."

"Mental is what happens when you suddenly start speaking French or become addicted to the smell of engine oil. This is physical brain alteration. And one comatose body."

"Why is it that when you say body, I hear corpse?"

Before the conversation could degenerate, Carter's radio went off. "Carter, this is Lupo, over."

"I'm here, over."

"Problem out at Fargo's place. Some take-home experiment getting violent. Over."

"On my way."

Nathan added, "over," without thinking about it.

"Always ruining my fun," Jack groused, grabbing artillery on the way out.

The effects of the 'experiment' were visible long before they reached Fargo's house – blasts of light shot into the air and spirals of smoke were rising from the trees. Jack took off from the jeep at a run, ducking out of the way of wild blasts from what looked like a butchered smart car. Nathan valiantly resisted the urge to yell Fargo's name, and let Jack make his way to Lupo.

Jo was on one side of the field, Fargo on the other. Jo gave an explanation that Jack understood about half of, and Nathan filled in the rest. Fargo was trying to come to meet them, miming "Not my fault" as clearly as he could.

There was a flash of light and a high-pitched squeal and he moved before he knew about it. Arms curled protectively over Fargo's head, deep breathing with the rush of the dive through the air.

"Dr Stark?" Fargo asked tremulously.

"It wasn't me, you moron," Nathan said.

"You okay, Fargo?" Carter asked. Then: "It was a little bit you, Stark." He raised his gun – guaranteed electronic interference and a blast radius of six feet, just in case. The machine exploded and died.

Nathan stood up. "We need to get to Global Dynamics."

"Forty-five minutes of my job and you're giving up already?" Jack asked.

"I think we could be in trouble."

- - - - -

"Your minds are bleeding together." Alison asked – again.

Jack answered her, because Nathan was too busy with the equations. "Apparently."

Henry was back, nodding at whatever Nathan was writing down. "It makes sense. We've been assuming that Jack is just taking up unused space in Nathan's brain. It's the ten-percent limit, and we've been working under the assumption that all that's happened is that now he's at twenty."

"But?"

"The human brain is a computer we are nowhere close to fully understanding. It adapts, it heals, and, crucially, it makes cross-links. The brain is starting to make use of both sets of expertise without needing to consciously consult the other half."

"Oh for God's sake, Nathan!" Jack said, taking control of the pen hand. He corrected the equation Nathan was fighting with.

He turned around to find Alison and Henry staring, while Nathan's thoughts were mixed indignation and amusement. "Oh crap."

"On the plus point," Alison tried, reaching, "There's a lot of scope for research here. I mean, with access to Nathan's knowledge, Jack's clearly capable of making the same kinds of intuitive leaps. The possibilities for development are…"

"Name me one thing." Jack said.

"You could send one person into a situation that would normally require a whole team. They could use their shared knowledge without even having to speak."

"Military operations."

"Not only…"

"And what happens when your seven-person-man gets shot? Like Nathan nearly managed this morning. They all die, right?"

"Well…"

"So lets worry about research into the benefits of collective consciousness when my brain isn't being assimilated into Stark's."

Nathan scowled. "Why do you automatically assume I'm the bad-guy? Maybe you're the one taking over _my _brain."

Henry raised a hand. "I've got it."

- - - - -

"Explain this to me again," Jack asked.

"Diffusion gradient." Henry said. "You were both pulled into the machine. Empty vessel, two full minds. Jack lets go, Nathan doesn't. Full vessel, empty mind. Then the electronic interference happens and it thinks it has hundreds of minds. It funnels both of you back into Nathan, because it thinks that's what it's supposed to do. All we need to do is recreate the interference from the other side."

Jack sounded unconvinced. "Seriously?"

Nathan rubbed his head. "Just trust me, Jack. It'll work."

"Okay, but what you're actually thinking is that there's a five percent chance we die and a fifteen percent chance this is permanent."

"Jack," Alison began reassuringly. Zoe, standing beside the bed, clenched her hand around his.

"No, don't worry about me, go ahead," Jack said.

Henry pressed the button, and the world blurred.

Nathan closed his eyes, and by the time they were opened, the headache was gone and he knew.

Zoe pulled her hand away from his. Not rudely, or even sharply, just a darting move away from him and back to Carter. She peered anxiously into Carter's eyes. "Dad?"

There was a split second where Nathan knew Carter was contemplating making a bad joke. Instead he grinned and squeezed her shoulder gently. "Right where you left me."

"Dad!" Zoe responded to this show of parental affection by punching her father in the arm. It might have been a better cover if she had not immediately followed it by leaning over Carter and wrapping her arms around him, face squashed up against his neck.

She turned around after a moment, eyes surprisingly astute. "Nathan?"

If anyone in the room was shocked by her familiarity, none showed it. "Yes?" he asked.

"You're alright?"

"I'm fine. Except for being three days behind on projects vital to our next funding meeting. Excuse me."

He pulled the pads from his head and left the room.

- - - - -

It was three days later. Nathan hadn't even been seriously thinking about it, but here he was in Jack's office.

Jo looked up. "He's at Vincent's."

"I didn't…"

She shrugged. "That's where he is. Take it or leave it. Oh, he's alone."

Jack was sitting at the counter, and Nathan tried to convince himself that he wasn't being watched when he sat down beside the sheriff. The stools were too close together, and their arms brushed.

"It's kind of a pity, actually. I bet we would have killed at baseball," Jack non sequitured.

At least that got the awkwardness out of the way. "I'm sorry?"

"I mean, I've never seen you play baseball, but the math stuff has to help, right? So between your genius, and my skills, I bet we would have wiped the floor with the rest of them."

Nathan grinned. "I actually don't need your 'skills' to play baseball."

"Really?" Jack asked. "I'll bear that in mind next time. You should get involved more, you know that?"

The silence was mostly comfortable. It was probably the first conversation they'd had (from separate bodies) without a pretext.

Vincent put a coffee down in front of Nathan, and refilled Jack's with a knowing look. Jack stretched for his, and after he pulled back, they were sitting hip-to-hip and elbow-to-elbow.

"How's Zoe?" Nathan asked.

Jack turned his head to look at Nathan, and his smile was wide open; almost as easy to translate as before. "She did great in her History of Science paper."

"I'm glad. She's a smart kid."

Jack's smile got even wider. "She told me to say thanks when I saw you. But you've been keeping a low profile. No explosions or anything."

"I had some thinking to do."

Turning serious, Jack looked away from him, towards the wall. "About what you saw?"

"To a degree."

"I can't…"

"I know you can't tell me. Or you don't want to, and I saw enough to understand why."

And he had stopped looking after that, no matter how easy it was. He could have looked for the answer to this question, but it didn't seem _right _somehow. Certainly it would have removed the challenge. "So I'm going to forget I saw it. It didn't happen."

Jack thought for a beat and then said, "No, it didn't. I don't remember much quantum physics now, but even I get that."

"So."

"So… what?"

"Nothing." Nathan stood up, getting ready to leave.

He had got maybe three paces from Carter when he heard, "Nathan."

"Yeah?"

"Zoe's dying to show you that essay of hers. Maybe you want to come round and take a look?"

Nathan nodded, surprised, but with no show of indecision. They matched their steps on the way out, too easy after so much more complicated space-sharing.

Jack beat a hand against his leg. "Oh, I forgot."

"Yes?"

"Well." Jack's expression was one Nathan had never thought to see on their Sheriff. "Zoe's actually at a friend's house tonight. If you still want to…"

"It would be just us? Well, I'm sure we'll find something to do."

Jack grinned, and held the door of his car open. "You know what? I actually sort of missed you."

* * *

FIN. Reviews are always appreciated. 


End file.
